The present invention relates to a light emitting diode (LED) unit employed in a photographing apparatus having an auto-focusing system.
Conventionally, in an auto-focusing system employing a triangular distance measuring system, a light emitting device as shown in FIG. 9 is employed. The auxiliary light emitting device is arranged, for example, aside from a photographing lens of an auto-focus camera. The light emitting device shown in FIG. 9 is provided with an LED (Light Emitting Diode) unit 1, and a projection lens 3. Infrared light emitted from a light emerging surface 2 of the LED unit 1 is projected towards an object through the projection lens 3. The light reflected by the object is received by a photo sensor accommodated in the camera. Then, depending on the position at which the reflected light is received, a distance to the object is determined.
FIG. 10 shows an another example of the light emitting device, which is used as an auxiliary light emitting device of a camera employing a phase-contrast distance measuring system. In the light emitting device shown in FIG. 10, a predetermined chart 4 is further arranged between the light emerging surface 2 of the LED unit 1 and the projection lens 3. When the LED unit 1 emits light, an image of the chart 4 is formed by the projection lens 3 on a plane at a predetermined position in front of the projection lens 3. The light reflected by an object in front of a camera is received through a photographing lens of the camera, and then the phase-contrast distance measuring method is applied to determine the focusing condition.
In the conventional auxiliary light emitting devices, however, the LED unit 1, the chart 4 (when used) and the projection lens 3 are constituted as separate elements. Therefore, it is difficult to make the auxiliary light emitting device compact, and further, it is troublesome to adjust distances between the elements when they are assembled.